Apparatus for recovering and recycling animal waste

ABSTRACT

A method and apparatus for recovering and recycling animal waste materials permits the separation of the solids with a desired moisture content from the remaining liquids and finer solid particles and wherein the liquids and finer solid particles are converted into a high quality single cell protein by means of aerobic digestion so as to maximize the value and percentage of total solids reclaimed as well as to maintain excellent sanitation and minimize odors from anaerobic decomposition. The animal waste material is delivered from the barn or other suitable collection area by aerated aerobic water onto an inclined separator screen, at which point the waste material is incrementally advanced along the screen by a combination of shuttle-driven scraper blades and pressure pads so as to cause the excess moisture or liquid together with a minimal amount of the finer solids to pass through the separator screen while advancing the rest of the material off the end of the screen and from which it may be conveyed to a separate holding area. The separator mechanism of the present invention permits a larger percentage of the finer solid particles to attach to and remain with the larger solid particles which are recovered whereby to substantially increase the total digestible nutrient value of the solid waste material removed.

This application is a divisional application of Ser. No. 133,534, filedMarch 24, 1980, for METHOD FOR RECOVERING AND RECYCLING ANIMAL WASTES,invented by Gerald P. Frankl, now U.S. Pat. No. 4,338,337.

This invention relates to a novel and improved method and apparatus forseparating liquids and solids and more particularly relates to a noveland improved method and apparatus for recovering animal feed values fromanimal wastes and which is specifically adaptable for use in a closedsystem.

BACKGROUND AND FIELD OF THE INVENTION

It has been found in the past that a high percentage of animal wastematerials can be converted into valuable animal feed and that such canbe accomplished in a closed system without chemical treatment. Forexample, in my prior U.S. Pat. No. 3,982,499, I have disclosed an animalwaste conversion and recovery system which has particular utility inlivestock feeding in a confinement facility. As described in my patent,the waste material is flushed from the barn into a sump or basin, fromwhich it is then pumped onto a wedge wire screen filter to separateexcess liquid from the solid materials: and additional liquid isseparated by means of a rotary press at one end of the screen so as tocompress or squeeze excess moisture from the solid material as apreliminary to collection of the remaining solid material in a separateholding area. Any liquids and fine solid particles which pass throughthe screen are delivered into an aeration tank for aerobic treatment.The aerated liquid and waste material are then recycled through theconfinement facility to aid in flushing additional waste materialtherefrom into the sump.

It is recognized that livestock convert a relatively low percentage offeed consumed into weight gain, the remainder being passed through theanimal in the form of excrement. For instance, in the case of beefcattle approximately 28% of the feed consumed by beef cattle on afattening ration is digested or utilized, and the remainder is passedthrough in the form of excrement. Accordingly, there is a tremendouseconomical potential not only in reclaiming the undigested solid portionof the feed, but also to increase the concentration of the totaldigestible nutrients in the feed.

In animal waste conversion systems now in use, such as, those disclosedin my prior patent, generally the percentage of total digestiblenutrient value in the recovered waste has been found to be relativelylow and can be largely attributed to the failure to retain many of thefine solids in the waste material, or solids which are not filtered outin the separation stage. A good percentage of highly digestible proteinsof high energy source are to be found in the fines or finer solidparticles of the waste material and, if separated from the solid wastematerials along with the excess moisture or liquid will greatly reducethe total digestible nutrient value in the solid waste materialrecovered. On the other hand, if some of the valuable and extremely finesolids are filtered through the screen with the excess moisture the finesolids will enhance the aerobic biological digestion process in theaeration tank. In other words, it is extremely important to strike aproper balance between the amount of fines permitted to pass through thescreen with the liquids and the amount of oxygen induced into theaeration pit for the biological conversion of the fine solids which dopass through the screen, into single cell proteins. The high percentageof the solids which are removed are for conversion into semi-dry feedsupplement. The moisture content of the solids removed is the means ofharvesting, and is a part of the single cell protein which is derivedfrom the biological digestion of the fine solids which are taken throughthe screen passing into the aeration tank.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide for anovel and improved method and apparatus for the efficient recovery andconversion of animal waste into animal feed values and whereinconversion takes place in such a way as to realize the highest ormaximum concentration of total digestible nutrients.

It is another object of the present invention to provide for a novel andimproved method for producing livestock feed supplements in a closedsystem which is readily conformable for use with various differentlivestock confinement facilities and yet permits recovery, conversionand reclamation in a minimum number of steps while maintaining maximumsanitation and being substantially odor-free.

A further object of the present invention is to provide for a novel andimproved separating apparatus for selectively filtering selectedpercentages of solids and liquids from animal waste materials in such away as to maximize the conversion of fine solids into a high qualitysingle cell protein, rich in amino acids which is continuously harvestedin the moisture content of the solids recovered or filtered from thewaste material and recycling same to serve as a carrier medium foradditional waste material and in such a way as to enrich the total feedrecovered.

It is a further object of the present invention to provide for a noveland improved shuttle-type separator capable of incrementally advancing aslurry of liquid and solid materials across a screen and selectivelyremoving a predetermined percentage of liquids and solids from theslurry as it is advanced thereacross while continuously cleaning thescreen, and to accomplish same in a reliable but highly simplifiedmanner.

In accordance with the present invention, there has been devised in apreferred embodiment thereof a closed system for recycling livestockwastes and converting same into animal feed having a maximumconcentration of total digestible nutrients. The method and system ofthe present invention is conformable for use with various types oflivestock confinement facilities but is best typified by describing itsuse in connection with hog and cattle barns wherein the waste materialis collected in gutters in the barns and can be periodically flushedfrom the barns into a sump or basin as a preliminary to pumping thewaste material to a separation stage. In the separation stage, the wastematerial is deposited at one end of an inclined screen having a limitedmesh or opening size, the screen being inclined upwardly in a directionaway from the point of deposition. A shuttle-type separator is suspendedabove the screen and includes a series or rows of scraper blades orwipers arranged at spaced intervals and in a direction transversely ofthe length of the screen. Interspersed at selected intervals butpreferably toward the trailing end of the screen opposite to the pointof deposition are rows of pressure pads which cooperate with the scraperblades in advancing the material across the screen as well as tocompress a predetermined amount of moisture with a limited amount offines from the solid waste material for recovery in a separate aerationstage or tank. The scraper blade and pressure pad assembly are operatedin unison by an eccentric cam and linkage assembly, the latter beingoperative to convert the rotary motion of the cam into a linearto-and-fro motion so that the blades and pressure pads are caused to belowered into engagement with the screen, advanced a limited distanceacross the screen to incrementally advance the waste materials, then areraised and reversed in direction back to their starting point toincrementally advance the waste materials over the next interval orlimited distance across the screen. The pressure pads are located towardthe trailing end of the screen and, depending upon the characteristicsand nature of the waste material, the number of pressure pads can bevaried in order to compress and force any excess moisture along with asmall amount of fines from the waste material prior to delivery off theend of the screen into a separate holding area; and furthermore theupper drive linkage for the pressure pads is preferably designed toimpart a more positive pressure and advancing motion than the lowerlinkage for the scraper blades. The scraper blades will cooperate tosome extent with the pressure pads in effecting partial compression andremoval of excess liquid and fines during the early stages of movementof the waste material across the screen. In this relation, it has beenfound that incremental advancement coupled with selective compression ofthe waste materials greatly improves the control and efficient recoveryof the desired amount of liquids and fines from the waste material forseparate recovery in the aeration tank.

In the aeration stage preferably a submersible air inductor assembly isemployed to most efficiently and continuously aerate the material so asto bring about the most complete aerobic digestion of the fines andconversion into single cell proteins. This liquid bio-mass is thenrecycled and employed as a flushing agent through the gutters of theconfinement facility, or facilities, to recover additional wastematerial and to carry it into the aeration tank. The waste material sorecovered can be conveyed or advanced at will into a separate storagefor efficient recovery and recycling of the waste materials in themanner described.

The method and system of the present invention have been found to beextremely efficient and versatile. Specifically the separation stage isadaptable for use in connection with waste conversion with one or moreconfinement facilities or barns, either independently or simultaneously.For example the system may be employed with cattle or hog barns eitherof the flow-through or flume type.

The above and other objects, advantages and features of the presentinvention will become more readily appreciated and understood from theforegoing detailed description of a preferred embodiment when takentogether with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevational view of a preferred form of mechanicalseparator in accordance with the present invention;

FIG. 2 is an end view of the separator shown in FIG. 1;

FIG. 3 is a top plan view of the preferred form of separator shown inFIG. 1;

FIG. 4 is a view in more detail of the shuttle-type drive employed inthe separator of the present invention;

FIG. 5 is a sectional view taken about lines 5--5 of FIG. 1;

FIG. 6 is a sectional view taken about lines 6--6 of FIG. 1;

FIG. 7 is a plan view of a preferred form of scraper blade and pressurepad assembly employed in the separator of the present invention;

FIG. 8 is a front view of the assembly shown in FIG. 7;

FIG. 9 is a cross-sectional view in detail of one of the wipers shown inFIG. 8;

FIG. 10 is a view in detail illustrating the spring loading of one ofthe pressure pad members and its mounting with respect to the separatorframe; and

FIG. 11 is a somewhat schematic view illustrating the sequence of stepsand arrangement of the various stages in an animal waste recovery methodwhen carried out in association with a pair of confinement facilities.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred method of the present invention is illustrated in FIG. 11wherein broadly a waste treatment station 10 is provided for therecovery and conversion of animal waste into animal feed values theanimal wastes being delivered from a plurality of livestock confinementfacilities. For the purpose of illustration and not limitation thelivestock confinement facilities may suitably comprise a flush flumecattle barn represented at 11 and a flow through, flush-type hog barnrepresented at 12. The cattle barn 11 corresponds to that described inmy hereinbefore referred to U.S. Pat. No. 3,982,499 in which a returnline 13 delivers flush water from the waste treatment station into aflow splitter box 14, the latter being divided into as many parts asthere are flumes or surge tanks 15 which traverse the length of the barn11. The flumes are sloped downwardly away from the flow splitter box sothat flush water delivered via the return line 13 will be evenlydistributed across the flumes so as to carry animal waste materialdownwardly along the flumes into a collector trough 60 from which thewaste-laden flush water can be delivered through line 17 into a sump 18at the waste treatment station. Similarly, a flush water return line 13aextends to the upper end of the hog barn 12 to deliver the flush waterinto a weir or flush tank represented at 20. The weir causes the flushwater to be spread evenly across the floor under the slotted grate 22which traverses the entire length and breadth of the hog barn; and in amanner similar to that described with reference to the cattle barn 11will carry the animal waste material collected by gravity feed to thelower end of the hog barn 12 where it is free to pass by gravity througha standpipe or drain represented at 24 into a delivery line 17A whichextends into the sump 18 of the waste treatment station.

By way of illustration in the conventional type of flow-through hogbarn, the weir 20 would extend across the end of a pit about 5" abovefloor level and is provided to spread the water evenly across the widthof a pit for even distribution across the breadth of the slotted pitfloor or gutters in the hog barn. The standpipe 24 at the lower end ofthe barn may for instance be on the order of 4" or 5" high so as tocause 4" or 5" of flush water to cover the floor at all times. Theamount of flush water required to carry the manure solids out on acontinuous basis and not permit any gases, odors or build up of solidsis calculated by determining the amount of water being retained in thepit. For instance, in a pit which is 6' wide by 120' long and it isdesired to retain 5" of water over the floor, a total of 2,214 gallonsof flush water would be required to adequately cover the floor.Generally, this flush water in the barn should be displaced on the orderof every three hours so that 12.3 gallons per minute is required to flowthrough the hog barn.

In the flush-type hog barn 12 a standpipe would not be required toretain any water. Instead the weir 20 in combination with the pitoperates as a flush tank to hold sufficient water so that, when releasedby a suitable valve at the bottom of the tank it will flush the wasteaccumulation from the slotted grate at periodic intervals. In order tocalculate the amount of flush water required for a barn which is 6' wideby 120' long and, assuming that 75 gallons per foot of width per 100' oflength is required, a total of 540 gallons would be necessary toperiodically flush the barn. If the barn is to be flushed every thirtyminutes, 540 gallons divided by thirty minutes equals 18 gallons perminute in each flushing cycle.

In the flush flume cattle barn 11, generally it has been found moredesirable to run the flush water continuously through the barn. For abarn which is provided with a series of four flumes, approximately 20gallons per minute per flume is required to adequately flush the barn,or a total of 80 gallons per minute. The length of the barn is not afactor since a barn 100' long would require the same amount of flushwater as a barn 1,000' long. With increasing length, however, it will beapparent that the amount of waste or solids per gallon would beproportionately greater. The collector trough 16 at the lower end of thebarn merely collects the waste-laden flush water from the four flumesand directs it through the delivery line 17 into the sump 18 at thewaste treatment station where it is collected along with the wastematerial recovered from the hog barn 12.

A submersible pump represented at 25 is suspended in the sloped bottomsump 18, and the pump 25 may suitably be a high volume low pressurecentrifugal pump which is activated by a float switch, not shown, sothat when the waste material in the sump 18 reaches a certain level itwill be pumped into a primary separation stage 28. The primaryseparation stage 28 may be nothing more than an inclined screen orseparator which slopes away from the discharge end of the conduit ordischarge line 25' from the pump and correspond, for example, to thewedge wire filter screen described in my aforementioned U.S. Pat. No.3,982,499. It should be pointed out that the primary screen or filter 28is required more for large operations, for example, those carrying overapproximately 3,000 head of hogs or 500 head of cattle. In smalleroperations. no preliminary filtration or primary separation stage 28 isrequired, and the waste-laden flush water is pumped directly to thelower end of a mechanical shuttle separator 30 to be hereinafterdescribed. Broadly, the separator 30 selectively removes a preselectedamount or percentage of liquid and fines from the waste material anddrains the same into an aeration tank 32. The larger solids arecollected off of the upper end of the screen of the separator 30 andpassed onto a conveyor 34 for removal of the solids into a stacking arearepresented at 35.

An air inductor assembly as represented 1 at 36 is employed in theaeration tank 32 and preferably is an air inductor assembly as describedin U.S. application for patent Ser. No. 849 965, filed Nov. 9, 1977. Theair inductor assembly 36 is capable of aerating the liquids and solidswhich pass through the primary filter 28 and the mechanical shuttleseparator 30 into the aeration tank 38. The air inductor assemblyfunctions in a unique manner to induce air to flow from the surfacethrough a venturi-shaped discharge zone for intimate mixture with theliquids and solids then recycles same throughout the aeration tank so asto circulate and uniformly distribute the air or oxygen throughout thetank. By breaking down the air into micro-sized bubbles and uniformlydistributing it throughout the liquid and fine solids, the solidsselectively passed through the filter will be aerobically digested andhydrolized with the solids converted into single cell protein matter.The aeration process is preferably continuous irrespective of the rateof delivery of the separation and removal of waste materials into theaeration tank. An outlet 39 is provided for removal of any excess oroverflow from the aeration tank 32 into a suitable storage basin, suchas, a lagoon or holding tank. In addition, the aeration tank 32 isprovided with a submersible flush pump represented at 40 which maintainsthe desired flow of liquid or flush water from the aeration tank 32 backto the barns 11 and 12. The solid waste material which is not separatedor passed through the screen at the separator 30 is conveyed from theupper end of the separator into the stacking or holding area 35. In amanner to be described the moisture content of the solids is regulatedby the separator 30 and by the amount of pressure applied to the wastematerial as it is advanced along the separator.

An important feature of the present invention resides in the mechanicalseparator 30 which, as shown in FIGS. 1 to 11, is characterized byhaving a fixed, static or non-vibrating screen 40 and an upper,shuttle-driven wiper assembly broadly designated at 42 for incrementallyadvancing waste material across the screen 40 in such a way that thelarger and more fibrous particles can operate as a filter or media forattachment of the fine solids, or fines, thereto so as to essentiallyremain within the mass of coarse solids as the excess moisture or waterpasses through the screen 40. Essentially, by avoiding the necessity ofvibration to effect separation of the liquids and solids, it is possibleto retain a much higher percentage of the fines within the coarser solidmass which is delivered from the end of the screen. At the same time, asmall percentage of the extremely fine solids will pass with the liquidthrough the screen, these fines being the undigested or partiallydigested particles of soybean meal or other protein supplement whichwere used in supplementing the ration fed to the animals or in somecases may constitute powdered fractions and finely ground grain, againcontaining more starch, sugar and energy than the larger particles, suchas, hulls from the grain or stems of the hay or silage being fed in aration. Generally, the larger particles are more bulky, fibrous andlighter in weight and contain less protein and energy; whereas the finesgenerally constitute the most valuable part of the waste solids. It istherefore important to control the relative percentages or proportionsof fines which pass through the screen in relation to that percentagewhich remains attached to the coarser solids which are delivered off ofthe end of the screen. To this end, and as illustrated in FIGS. 1 to 3,the screen 40 is of elongated, generally rectangular configuration andis preferably comprised of wedge wire screen sections having a mesh sizein the range of 0.005" to 0.002" which are laid in side-by-side relationwithin the bottom of a separator trough 44. The trough 44 is ofelongated, generally rectangular configuration having opposite endswalls 46 and 47 and sidewalls 48 and 49, an upper flange 50 extendingaround the upper periphery of the trough and a bottom wall 52 whichslopes downwardly into a generally funnel-shaped drain or sump pan 53. Asloped shelf 47' inclines downwardly at one end 47 toward the lowerscreen section of the screen 40, and the opposite end 46 has a verticalwall.

Preferably, the trough 44 is adjustably suspended from a main frame 54which is comprised of an upper, open rectangular frame portion 55vertical legs 56 at the four corners of the frame and lower horizontallyextending brace members 57 which make up a lower, open rectangular frameinterconnecting the leg members and rigidifying the entire structure.The legs 56 are provided with vertically adjustable feet 58 to permitsome limited adjustment of the height of the frame. Suitable braces areprovided to further rigidify the frame including upper diagonal braces59 across the corners of the upper frame, gusset plates 60 between thelegs 56 and upper frame 55; and additional braces, not shown, may extendalong opposite sides of the frame, for example, to run diagonally fromthe legs 56 between the upper and lower frames 55 and 57.

In order to adjustably suspend the trough 44 from the frame asdescribed, generally channel-shaped beams or side rails 62 extendbetween the legs at opposite ends of the frame and along opposite sidesthereof at an acute angle with respect to the upper frame 55. Cradles 64serve to adjustably support the upper edge of the trough in spacedrelation beneath the side rails there being a series of three cradles 64spaced along opposite sides of the trough and each having a main,vertically extending flange or plate 65 attached to one of the outersidewalls 48 or 49 of the trough, an upper plate member 66 attached tothe inside of the side rail 62, and an inwardly projecting pin 67 at thelower end of an adjustable block 68 is inserted into an opening by anupper sidewall 48' or 49' on each side of the trough. Each pin 67 issuspended by a threaded rod 69 from an upper, horizontally extendingsupport plate 70 at the upper end of the plate 66. Lock nuts 71 arethreadedly connected to the rod 69 above and beneath the plate 70 so asto adjustably control the height or positioning of each pin 67 and inthis manner regulate the spacing of the trough beneath the side rails,and scraper blade assembly, 62. Each of the cradles 64 can beindependently adjusted to control the attitude or inclination of thetrough with respect to the inclined side rails but are essentiallymounted in such a way as to suspend the trough in spaced parallelrelation to the side rails 62 so that the separator screen is inclinedupwardly away from the point of deposition of the waste materials fromthe primary filter.

In order to advance the waste material at a smooth, gentle pace alongthe screen so as to retain a very high percentage of total solids in thewaste material delivered from the upper end of the screen, the wiperassembly 42 is suspended from the upper shuttle drive 76 for linearto-and-fro movement across the screen. The wiper assembly 42 comprises amain frame 78, which as shown in FIG. 5, includes a pair of spaced,parallel, longitudinally extending beams 79 which are interconnected atopposite ends by subframe assemblies 80, each subframe having atransversely extending angle iron 81 to which the ends of the beams 79are affixed, and outboard angle irons 82 which extend from oppositecorners of each crossbeam 81 and have inward, angularly extending returnmembers 83 permanently affixed to each of the respective beams 79. Asubframe 84 of generally rectangular configuration is superimposed uponthe main frame to extend along the greater length of the main frame froma point adjacent to the lower end of the main frame 76. An uppersuspension frame 85 is attached to the upper end of the subframe 84 anda lower suspension frame member 86 is attached to the lower end of thesubframe 84 the suspension members 85 and 85' serving as the motiontransmitting elements between the upper shuttle drive 76 and wiperassembly 42 in a manner to be hereinafter described.

As a preliminary to describing the shuttle-type drive system, referenceis made to FIGS. 6 to 11 which illustrate in detail the manner in whicha series of scraper blades 86 and pressure pads 86' are suspended fordownward extension from the main frame of the wiper assembly. The blades86 are arranged for transverse extension at closely-spaced intervalsalong the lower end of the frame followed by a series of transverselyextending pressure pads 86' extending in spaced parallel relation alongthe upper length of the frame, and a single blade 86 is positioned atthe upper edge of the frame 76. Each wiper or scraper blade ispreferably in the form of a paddle 88 of generally rectangularconfiguration and composed of a rubber or rubber-like material which issuspended from the main frame or beam member 79 by a plurality of lagbolts 89 extending downwardly through each frame 79 and each terminatingin a threaded shank which is inserted into a threaded sleeve or socket90 at the upper extremity of the paddle 88, and a lock nut 91 is wedgedinto a shallow recess or seat 92 at the upper edge of the sleeve 90 asspecifically illustrated in FIGS. 7 to 9. Compression springs 93 aremounted on the frames 79 in surrounding relation to the bolts 89 toyieldingly urge the bolts 89 and attached scraper blade downwardlyagainst the screen 40.

The pressure pads 86", as shown in FIGS. 10 and 11, are each in the formof a horizontally extending block 94 having a downwardly projecting,tapered lip or rib 95 of generally triangular configuration. Each block94 is composed of a rubber or rubber-like material and is suspended fromeach beam 79 by a pair of lag bolts 96 extending downwardly through theframe and having lower threaded shank portions inserted into the upperend of each block 94. Preferably, each block 94 is reinforced by a metalplate 98 which is sandwiched between the upper surface of each pad andthe upper pad portions 97. Lock nuts 99 are tightened against the upperend surfaces of the pad portions 97 to positively but releasably securethe bolts 96 in place to the pads while leaving a limited space betweenthe bottom surfaces of the beam 79 and the lock nuts 99 for limitedvertical movement of the bolts and attached pad with respect to thebeam. The pads 94 are yieldingly urged downwardly away from the beams 99by means of leaf springs which for example may be of the typeillustrated at 100 in FIG. 10 with the upper free ends 102 engaging thehead ends of the bolts 96 so as to bias the bolts downwardly against theupper or top surface of the beams 79. In the alternative, compressionsprings 93 of the type employed on the paddles 88 may be used in placeof the leaf springs 100, as shown in FIG. 5. In either form, the wiperassembly 76 comprised of the scraper blades 86 and pressure pads 86' arespring-loaded so as to be urged downwardly into engagement with theupper surface of the screen under the control of the shuttle drive 76.

In order to impart the desired linear to-and-fro movement to the wiperassembly 42, the preferred form of shuttle drive 76 employs an eccentriccam 110 which is mounted for rotation on a drive shaft 112, the latterrotated by a motor drive represented at M through a gear reducer Gsupported on a pillow block 113 on one side of the frame. Preferably,the motor drive is capable of generating up to 1750 rpms to the inputside of the gear reducer which has a gear ratio on the order of 100:1 soas to reduce the speed of the drive shaft to the range of 12 rpms to 20rpms. The cam 110 has an outer peripheral surface which receives a pairof upper and lower, arcuate bands 115 and 116 which are clamped togetheras at 115' and 116', respectively, and are free to ride in a channelformed between an outer flange portion 117 on the cam and a retainingring 118 which is bolted to the front face of the cam. An uppergenerally triangular cam arm 119 is pivotally secured as at 120 directlyto a surface of the cam 110 on the side opposite to the ring 118. Asshown in FIGS. 3 and 4, the opposite end of the cam arm is pivotallyconnected by a support bracket 121 to the upper end of a downwardlydirected, upper primary lever 122 which is pivoted at its lower end 123to a fixed support bracket 124. A downwardly extending portion 125 ofthe cam arm has its lower end 126 pivotally connected to upper secondarylink bar 127, the link bar 127 being pivotally mounted at 128 to theupper end of upper suspension frame 85 which extends upwardly from fixedconnection to the subframe 84 of the wiper assembly 76. A compressionspring 130 is mounted in a capped sleeve 131 with a spring-tensionadjustment bolt located at the top of the sleeve which extends in spacedparallel relation to the upper suspension frame 85. The compressionspring acts on the upper secondary link bar 127 to yieldingly apply adownward pressure to overcome the spring tension created by the springs93 and 100. The spring 130 also yieldingly resists any tendency of theupper suspension frame 85 to rotate about the upper pivot 128; or, inother words, to rotate with respect to the upper secondary link bar 127.

The lower cam drive linkage is coordinated with the upper cam drive toimpart synchronized linear to-and-fro movement to the lower end of thewiper or brush rack assembly 76. To this end, the lower linkage systemincludes a lower cam arm 132 which is angled first upwardly, thendownwardly at a gradual angle away from the band 116 and is pivoted at133 to a lower primary lever 134 which in turn is pivoted as at 135 to afixed support bracket 136. The lower primary lever 134 is somewhat inthe form of a bell crank having a lower arm 134' inclining downwardlyand away from the pivot 135 for pivotal connection as at 138 to alinkage bar 139, the upper end of which is pivoted as at 140 to asecondary link bar 141. Link bar 141 is in turn pivotally attached as at142 to a lower suspension frame 85' which is affixed to the lower end ofthe subframe 84. Another compression spring 130 and rod 131 are securedbetween the lower suspension frame 85' and link bar 141 to yieldinglyresist rotational movement of the lower frame 85' about the pivot 142and to apply downward pressure yieldingly to overcome spring tensioncreated by the springs 93.

The bands 115 and 116 for the lower cam arm 132 are clamped together soas to permit the cam 110 to rotate the upper cam arm 119 independentlyof the lower arm 132, the latter following the eccentric motion of thecam about the axis of the shaft 112. As a result, the cam arms willimpart coordinated pivotal movement through the linkage systems asdescribed to cause the wiper assembly 42 to undergo a cycle of movementin which the scraper blades 86 and pressure pads 86' first are advanceddownwardly into contact with the screen, move in a linear direction fora limited distance along the screen, then are gradually raised away fromthe screen and reversed in movement back to the original starting pointon the screen. Although the movement of the wiper assembly can begenerally characterized as a linear to-and-fro movement, it will followthe path, as represented in dotted form at 146 and 147, for the upperand lower ends of the wiper assembly, respectively. The upper linkagesystem as described, in following the rotational movement of the cam110, imparts a somewhat greater pressure through the pressure pad rows86' than is imparted through the scraper blades 86, by regulating therelative spring tension of the springs 93 for the pressure pads 86' andthe scraper blades 86. In this way, progressively increased pressure isexerted on the waste material in removing liquid therefrom as it isintermittently advanced along the screen. In the manner described, thescraper blades 86 and pressure pads 86' achieve the two-fold purpose ofdrawing the residual solids that remain on the screen together in ridgesin front of the blades and pads as the free water and limited percentageof fines pass through the screen and, in so doing, constantly clean thescreen openings so as to permit the free water to pass therethroughafter repeated use. By imparting intermittent advancement to the solidsalong a stationary screen with the wiper elements, a higher percentageof total solid content is retained in the waste material and only asmall amount of the solids, i.e., the solids smaller than the mesh sizeof the screen, are permitted to pass through with the water, since mostof the finer solids will attach themselves to the larger solid matter.Those solids which pass with the liquid into the aeration tank aresubjected to aeration by injecting a large volume of air into the flushwater and through an extremely high rate of pumpage and mixing action,the micro-sized air bubbles formed are continuously mixed throughout theentire body of flush water being held in the tank. This intensifies theaeration and affords the necessary oxygen for complete aerobic digestionof the relatively small percentage of fines or nutrient solids which dopass through the screen as a preliminary to returning the flush water tothe barns for carrying additional waste material back to the separator.In other words, the fine solids which do pass through the screen areconverted into high quality single cell protein which is rich in aminoacids and which can be continuously recovered in the moisture contenttaken of the solids from the surface of the separator screen.

The system as described is capable of harvesting in excess of 80% of thetotal solids coming from a given livestock operation. Not only is itcapable of harvesting an extremely high percentage of the total solidsrecovered from the end of the screen, but also harvesting the fines thatdo pass through the screen in the form of single cell protein which inturn enriches the feed recovered when the flush water is returned to thebarns to carry additional waste material back to the separator. Thesolids that are taken from the screen preferably contain on the order of70-72% moisture unless the management of the system dictates either alower or higher moisture content. The moisture content of the solidsbeing removed may be controlled within limits to the desired moisturecontent by setting the pressure exerted on the pressure pads in theupper portion of the wiper assembly and choosing the desired number ofpressure pads as described. A relatively low stream of fresh water maybe introduced into the system upstream of the separator, particularly ifa relatively high moisture level of solids is to be removed whilemaintaining the desired level of flush water in the system. On the otherhand, it is possible to sustain a small amount of overflow from thesystem if drier than average moisture solids are to be removed, such as,less than 70%.

It is to be understood from the foregoing that while a preferred form ofmethod and apparatus of the present invention has been set forth, itshould be appreciated by those skilled in the art that variousmodifications, changes and adaptations may be made without departingfrom the scope of the present invention as defined by the followingclaims.

I claim:
 1. Apparatus for separating a mixture of liquid and solidmaterials comprising:a lower receptacle; an elongated screen positionedover said receptacle, said screen having an opening size adapted topermit liquid and a preselected size of solid particles to pass bygravity therethrough; means for delivering said mixture of liquid andsolid materials and depositing said mixture of materials at one end ofsaid screen; and separator means operative to advance said mixture ofmaterials along the length of said screen including a series of scraperblades and horizontally disposed pressure pad members extending atspaced intervals along the length of said screen with each said scraperblade and pad member extending in a direction transversely of the lengthof said screen and pad having a broad surface portion in facing relationto said screen, and shuttle drive means operatively connected to saidscraper blades and pad members to continuously and repeatedly advanceand reverse said scraper blades and pad members in unison and in alinear to-and-fro movement lengthwise of said screen to successivelymove downwardly into engagement with said mixture of materials on saidscreen for a limited distance substantially less than the length of saidscreen, then be raised and reversed in movement to their originalpositions whereby to incrementally advance said mixture of materialsdeposited onto said screen across the entire length of said screen. 2.In apparatus according to claim 1, said screen being inclined in anupward direction away from the point of deposition of said mixture ofmaterials thereon.
 3. In apparatus according to claim 1, said shuttledevice means being operative to raise said scraper blades and padmembers above the surface of said screen preliminary to reversal and,upon reversal, to lower said scraper blades and pad members into contactwith said screen preliminary to forward advancement across the surfaceof said screen.
 4. In apparatus according to claim 1 said receptacleincluding a drain at one end.
 5. In apparatus according to claim 1, saidscreen being defined by a wedge wire screen having a mesh size in therange of 0.005 to 0.002 of inch.
 6. In apparatus according to claim 1,said separator means including a common frame from which said scraperblades and pad members are suspended, and said shuttle drive meansincluding an upper eccentric cam member and a pivot link assemblyinterconnecting said eccentric cam and said scraper blade frame toconvert the rotational motion of said cam into shuttle-type movement ofsaid scraper blades.
 7. In apparatus according to claim 1, said padmembers disposed at spaced intervals between and parallel to saidscraper blades, each of said pad members including a downwardlyprojecting lip at the leading edge of said pad member movable intoengagement with the surface of said screen.
 8. In apparatus according toclaim 7, said separator means including resilient means associated witheach of said pad members to yieldingly urge said pad members in adownward direction toward the surface of said screen.
 9. Apparatus forrecovering animal feed values from liquid/solid waste materials, saidapparatus comprising:a lower receptacle including a drain; an elongatedscreen member positioned over said receptacle; means for delivering saidwaste materials in slurry form and depositing same at one end of saidscreen; and shuttle-type separator means operative to advance said wastematerials along said screen including a series of scraper blades andhorizontally disposed pressure pad members extending at spaced intervalsalong the length of said screen, each said scraper blade and pad memberextending in a direction transversely of the length of said screen, saidscraper blade frame including means spring-loading said scraper bladesand pad members to yieldingly urge said scraper blades and pad membersin a downward direction toward the surface of said screen, and shuttledrive means operatively connected to said scraper blades and pad membersincluding a frame from which said scraper blades and pad members aresuspended, an eccentric drive cam including means for rotating saideccentric drive cam, and pivot link means operatively interconnectingsaid eccentric drive cam and said frame to convert the rotationalmovement of said eccentric drive cam into linear to-and-fro movement ofsaid frame to continuously and repeatedly advance and reverse saidscraper blades and pad members in unison and in a linear to-and-fromovement lengthwise of said screen to successively move downwardly intoengagement with said mixture of materials on said screen for a limiteddistance substantially less than the length of said screen, then beraised and reversed in movement to their original positions whereby toincrementally advance said waste material across the length of saidscreen.
 10. In apparatus according to claim 9 said screen having a meshsize to selectively permit removal of a portion of the liquid and finerparticles from said waste materials.
 11. In apparatus according to claim9, each said pressure pad member extending in a direction parallel tosaid scraper blades and including a downwardly projecting lip at one endthereof.
 12. In apparatus according to claim 11, said screen incliningupwardly and away from said one end of said screen upon which said wastematerials are initially deposited, and said pressure pads being arrangedin rows away from said one end of said screen.
 13. In apparatusaccording to claim 12, said separator means further including resilientmeans associated with said frame and engagable with said scraper bladesand pressure pad members to yieldingly urge said scraper blades andpressure pad members downwardly toward the surface of said screen.